In the preparation of multivalent conjugate pneumococcal vaccines directed to the prevention of invasive diseases caused by the organism Streptococcus pneumoniae (also known as pneumococcus), selected Streptococcus pneumoniae serotypes are grown to supply polysaccharides needed to produce the vaccine. The cells are grown in fermentors with lysis induced at the end of the fermentation by addition of sodium deoxycholate or an alternate lysing agent. The lysate broth is then harvested for downstream purification and the recovery of the capsular polysaccharide which surrounds the bacterial cells. After conjugation with a carrier protein, the polysaccharide is included in the final vaccine product and confers immunity in the vaccine's target population to the selected Streptococcus pneumoniae serotypes.
Polysaccharide size is a quality attribute that is assayed in each preparation batch and must be appropriately controlled. With respect to Streptococcus pneumoniae serotype 19A polysaccharides, the size of the polysaccharide can be affected by parameters such as fermentation pH, fermentation temperature, and hold temperatures. Furthermore, thermal degradation of 19A polysaccharides occurs across both fermentation/recovery and purification processes, which provides an additional challenge for successfully addressing and controlling various parameters when scaling-up production processes for the large-scale manufacture of 19A polysaccharides.
Accordingly, improved methods for the recovery of high molecular weight serotype 19A capsular polysaccharides from cellular Streptococcus pneumoniae lysates are needed.